The invention relates to an internal combustion engine with at least one cylinder with a reciprocating piston coupled to a connecting rod for rotating a crankshaft, with an engageable gear that is comprised of a first gear shaft that is driven by the crankshaft through a belt-type stepless transmission and of a second gear shaft that is coupled to an intermediate shaft for rotating a drive shaft, and with a balancer shaft driven by the crankshaft, said crankshaft, first gear shaft; second gear shaft, intermediate shaft and balancer shaft being disposed in one common, multi-piece housing.
Internal combustion engines of the type mentioned herein above serve to drive what are termed ATVs (All-Terrain-Vehicles), motorcycles and motor scooters. Engine and gearing are housed together in one multi-piece housing. Usually, the housing is divided in a plane normal to the axis of the crankshaft. This however has the disadvantage that machining and assembly of the housing pieces is quite complicated as a plurality of shafts are to be inserted simultaneously into corresponding shaft receiving bores provided in the housing pieces.